A sustainable water system reduces not only overall water consumption but also the associated energy demand. Take steps to optimize the system’s efficiency, implement water conservation measures, and integrate water reuse/recycling strategies.
Toilets and urinals attribute to approximately one third of the total building water consumption. Water efficient fixtures such as ultra-low flow, dual flush, pressure-assisted, or waterless technologies can lead to significant savings. Conventional toilets and urinals require 1.6 or 1.0 gallons per flush (gpf) respectfully, while their efficient counterparts use little (0.125 – 1.0 gpf) to no water at all. Utilizing non-potable water sources, such as greywater, for flushing further diminishes overall potable water consumption. Maintenance of flush valves is imperative, as a constantly running toilet can waste over 200 gallons of water each day.1
1. EPA WaterSense: The Facts on Leaks
Faucets and showers, like toilets and urinals, are areas where water efficient technologies can conserve significant volumes of potable water. Faucets and showers, however, require energy to heat the water to comfortable levels. As a result, reducing the amount of water needed for showering and washing hands also reduces energy use.
- Conventional showerheads and faucets deliver 2.5 gallons per minute (gpm).
- Low-flow showerheads with aerators mix water droplets with air to cover the desired surface area using less water (0.5 to 1.5gpm).
- Metered valves in faucets deliver a preset amount of water (usually 0.25 gallons per cycle) before automatically shutting off.
- Automatic sensor valves detect the presence of hands to ensure functionality only when needed, thereby limiting overall water flow.
As with all plumbing fixtures, maintenance is important to ensure continued water conservation; a leaky faucet dripping at a rate of one drip per second can waste more than 3,000 gallons of water annually.1
1. EPA WaterSense: The Facts on Leaks
Water used for landscaping and irrigation purposes accounts for close to 20% of a facility’s overall consumption and should be limited as much as possible through xeriscaping, water-efficient systems and schedule optimization. See FEMP BMP 4 and 5.
- Reduce the amount of irrigated areas and replace water-intensive plants with native or climate appropriate landscape materials (Xeriscape) to decrease or completely offset both water consumption and maintenance (i.e. fertilizer, pruning, mowing, and landscaping labor) costs.
- For outdoor areas needing irrigation, incorporate water-efficient systems such as low-flow sprinkler heads or drip irrigation systems that evenly distribute water.
- Optimize irrigation schedules and controls to deliver water to the landscape only as needed based on weather conditions.
Boiler and steam system equipment consume varying quantities of water within large heating systems depending on the size of the equipment, the amount of steam used, and the corresponding amount of condensate returned. As a result, it is important to properly size boiler and steam units according to the facility’s heat and steam requirements. Reducing these requirements leads to less makeup water needed in the system. Water supply and chemical use can be reduced up to 70% by recycling condensate for reuse within the boiler and steam units.1 Similarly, automatic blow-down systems based on detection of boiler water quality will more efficiently manage the removal of accumulated solids and/or sludge without wasting water. See FEMP BMP 8.
1. Federal Energy Management Program (FEMP) BMP 8: Boiler/Steam Systems
Single-pass (or once-through) cooling equipment uses water for only one cycle before subsequently discharging it. Examples of this equipment include condensers, air compressors, degreasers, vacuum pumps, ice machines, and air conditioners. In order to maximize water savings, single-pass systems should be eliminated altogether or be replaced or modified to operate on a closed-loop that recirculates water instead of discharging it. If a closed-loop alternative is not feasible, implementing an automatic shut-off valve and reusing the discharged water for non-potable situations are sustainable alternatives. To remove the same heat load, single-pass systems use 40 times more water than a cooling tower operated at five cycles of concentration.1 To maximize water savings, single-pass cooling equipment should be either modified to recirculate water or, if possible, should be eliminated altogether. See FEMP BMP 9.
1. Federal Energy Management Program (FEMP) BMP 9: Single-Pass Cooling Equipment
Water leaves the cooling tower system through evaporation, blow-downdrift, and basin leaks and overflows, and therefore has to be replaced. Since cooling towers by nature dissipate heat from recirculating water through evaporation, reducing the quantity of water lost to evaporation can be achieved through improving the energy efficiency of the systems being cooled. Blow-down, however, should be carefully monitored and controlled with conductivity meters to ensure dissolved solid concentrations are regulated without wasting water. Implementing baffles and drift eliminators limit the water losses attributed to mist being carried from the system, while checking float control equipment and valves ensures basin leaks or overflows are properly avoided. See FEMP BMP 10.
Harvesting systems capture water from rain or other sources and use this non-potable source to offset the consumption of water serviced from utility companies. Rainwater harvesting typically involves collection from the roof of the building. Coupled with a green roof, additional treatments to rainwater might not be necessary before reuse. Stormwater harvesting involves collection of water accumulated from access rain on surface ponds or basins and requires additional treatment. While this source is not safe for drinking in the office environment, popular end uses include landscape irrigation, and toilet flushing to offset potable water consumption and sewage discharge.
Gray water is the water stemming from processes such as showers, hand basins, or kitchen sinks but does not contain any human waste. Reusing gray water typically involves some form of basic solid filtration and microbial digestion treatments which permit the resource to be utilized in landscape irrigation and toilet flushing applications, thus reducing total potable water consumption. Gray water harvesting systems should comply with local health codes and ordinances.
Water efficiency measures do more than conserve water; they conserve a significant amount of energy as well. Federal facilities use sixty billion Btu of energy annually to process, heat, and distribute water throughout buildings. Of that, over 98 percent of that energy is used for heating water.1 Similarly on a national scale, eight percent of U.S. energy demand goes to treating, heating, and pumping water – equivalent to powering five million homes for an entire year.2 Conversely, it takes 3,000 to 6,000 gallons of water annually to power just one 60-watt incandescent bulb for 12 hours per day.3 Implementing a sustainable water system that leads to measurable water conservation, as a result, further benefits the facility’s overall energy management plan and reduces associated costs. Water conservation also means that less need be treated in the first place, reducing the embodied energy associated with purification and distribution across our water infrastructure.
To help move toward a more sustainable energy and water future, EPA has drafted Principles for an Energy Water Future (PDF).
1. Whole Building Design Guide (WBDG): Water Conservation2. EPA Buildings and their Impact on the Environment: A Statistical Summary3. Water: What You Can Do
